With development of mobile communications technologies and broadband wireless access technologies, services of the two interpenetrate. A technology, such as carrier aggregation (CA), is introduced into a mobile communications system, so as to meet a requirement of broadbandization of mobile communications and cope with a challenge from mobility of broadband communications.
With aggregation of multiple consecutive or non-consecutive component carriers in the CA technology, larger bandwidth can be acquired, so that a peak data rate and a system throughput are increased, and at the same time, an operator's problem of frequency spectrum discontinuity is also solved. User equipment (UE) is capable of separately supporting aggregation of multiple component carriers (CC) in downlink and uplink. The multiple aggregated component carriers include one primary component carrier (PCC) and at least one secondary component carrier (SCC). A carrier initially accessed by the UE is a PCC, and one or more other carriers are SCCs.
Layer 2 (L2) defined in the 3rd Generation Partnership Project (3GPP) protocol includes a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and a Medium Access Control (MAC) layer. After the CA technology is introduced, the SCC is visible only at the MAC layer, and the PCC and the SCC are not differentiated at the PDCP layer and the RLC layer. As a result, when data is processed at layer 2, a wait delay is introduced before the data is processed at the RLC layer, which makes it difficult to meet a real-time requirement.